Growth of the M. catarrhalis WT isolate O35E and tat mutant strains in liquid medium. Plate-grown bacteria were used to inoculate sidearm flasks containing 20-mL of broth to an OD of 50 Klett units. The cultures were then incubated with shaking at a temperature of 37°C for seven hours. The OD of each culture was determined every 60-min using a Klett Colorimeter. Panel A: Growth of O35E is compared to that of its tatA isogenic mutant strain, O35E.TA, carrying the plasmid pWW115 (control), pRB.TatA (specifies a WT copy of tatA), and pRB.TAT (harbors the entire tatABC locus). Panel B: Growth of O35E is compared to that of its tatB isogenic mutant strain, O35E.TB, carrying the plasmid pWW115, pRB.TatB (specifies a WT copy of tatB), and pRB.TAT. Panel C: Growth of O35E is compared to that of its tatC isogenic mutant strain, O35E.TC, carrying the plasmid pWW115 and pRB.TatC (contains a WT copy of tatC). Growth of the bro-2 isogenic mutant strain O35E.Bro is also shown. Results are expressed as the mean OD ± standard error. Asterisks indicate a statistically significant difference in the growth rates of mutant strains compared to that of the WT isolate O35E.